1. Field of the Invention
The present invention relates to a technique of manufacturing a semiconductor device. In particular, the present invention relates to immersion exposure method and apparatus, which can prevent substrate from being contaminated in an immersion exposure process of carrying out exposure in a state that a liquid is filled between a projection optical system of an exposure apparatus (stepper or scanner) and a substrate subjected to an exposure process. Moreover, the present invention relates to a manufacturing method of a semiconductor device.
2. Description of the Related Art
Recently, an exposure apparatus calling an immersion exposure apparatus and an exposure method calling an immersion exposure method of using the immersion exposure apparatus, have attracted special interest. The foregoing technique has been disclosed in JPN. PAT. APPLN. KOKAI Publication No. 10-303114, for example. In brief, the foregoing immersion exposure apparatus is an apparatus for exposing a resist layer in a state that a liquid calling immersion liquid is filled between the surface of the resist layer formed on a substrate to be exposed and a projection optical system of the exposure system. The foregoing immersion exposure method is a method of carrying out exposure using the apparatus for immersion exposure.
In a general immersion exposure apparatus, various devices and structures are arranged at an outer periphery of an exposure stage. Specifically, there are arranged equipment for measuring positional precision of an exposure state on which a substrate is placed, various wirings, principal devices and structures having a need to avoid a contact with immersion liquid. There is a high possibility that these devices and structures break down if they contact with the immersion liquid. For example, in the immersion exposure apparatus, a contact angle of the outer peripheral surface of the exposure stage with respect to the immersion liquid is set smaller. Specifically, in an immersion exposure apparatus using water as immersion liquid, the outer peripheral surface of the exposure stage is set in a state of having high hydrophilicity, that is, low water repellency. In this case, when exposing the outer periphery of a substrate to be exposed, immersion liquid is immersed in the outer periphery of the exposure stage. For this reason, the immersion liquid contacts with devices and structures arranged at the outer periphery of the exposure stage. Thus, there is a high possibility that these devices and structures break down. In order to solve the foregoing problem, the apparatus for immersion exposure has the structure given below. That is, a contact angle of the outer peripheral surface of the exposure stage to the immersion liquid is set very larger so that the immersion liquid does not contact with the outer peripheral surface of the exposure stage. Specifically, in the immersion exposure apparatus using water as immersion liquid, the outer peripheral surface of the exposure stage is set in a state of having low hydrophilicity, that is, a state of performing high water repellency.
For example, the contact angle of the surface of the substrate to be exposed with respect to the immersion liquid is smaller than that of the outer peripheral surface of the exposure stage. In this case, if the immersion liquid is positioned ranging over both exposure state and wafer, the immersion liquid is easy to be moved from the outer periphery of the exposure stage toward the substrate to be exposed. For example, the immersion liquid is further readily moved from the outer periphery of the exposure stage toward the substrate to be exposed in the following cases. One is the case of exposing the outer periphery of the substrate to be exposed. Another is the case where a projection optical system of an exposure system comes into an exposure state from an exposure standby state or a revise state such as exposure correction. Another is the case where the projection optical system moves on the outer periphery of the exposure stage. More specifically, the immersion liquid is further readily moved from the outer periphery of the exposure stage toward the substrate to be exposed in the following cases. One is the case where the immersion liquid exists on both surfaces of the substrate to be exposed and the outer periphery of the exposure stage. Another is the case where the projection optical system of the exposure system exists in the vicinity of the outer periphery of the substrate to be exposed.
In such a case, if impurity existing on the outer periphery of the exposure stage is covered with the immersion liquid, a possibility that the following phenomenon occurs is very high. Specifically, the impurity moves from the outer periphery of the exposure stage toward the substrate because it goes with a flow of the immersion liquid moving from the same as above toward the substrate. The impurity moves as described above, and thereby, the surface of the substrate to be exposed is contaminated. This is a factor of causing the following problem. That is, when exposing or forming a pattern, a possibility that defect occurs in the pattern becomes extremely high. As a result, performance, quality and reliability of semiconductor devices are reduced; for this reason, a rate of manufacturing defective products increases. In addition, the yield of the manufacturing process of the semiconductor devices is reduced.